>>6655335It was a big Bionicle villain concept.
The general idea was to run a non-lego tube through the larger tube and make some kind of squirt gun contraption in the body using technic and a non-lego bag of whatever liquid to essentially make it look like he spits acid. 
I drew a really rough concept about a year or two ago, but the idea never really took off. Maybe I'll start it eventually.